<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .parent{
            width: 100px;
            height: 100px;
            background-color: seagreen;
            border: 10px solid #000;
            padding:10px;
            /* box-sizing: content-box; */
            /*默认的标准盒模型，包括padding和border*/
        }
        .two{
            width: 100px;
            height: 100px;
            background-color: skyblue;
            box-sizing: border-box;
            /*怪异盒模型  不包含border和padding*/
            padding:10px;
            border: 10px solid #fff;
        }
    </style>
</head>
<body>
    <div class="parent">
    </div>
    <div class="two"></div>
</body>
</html>